1. Field of the Invention
This invention relates to a reproduction method and also to a reproduction apparatus adapted to transmit a first digital signal for main data of a piece of music and additional data accompanying the main data and including the number of the piece of music and the elapsed time on the track and a second digital signal for main data of the piece of music and accompanying absolute time data on a common digital interface.
2. Related Background Art
The digital audio interface output of known compact disk (CD) players is adapted to produce, in addition to main data that are digital audio data, channel status data including a category code for identifying the CD category of the CD disk to be played and user data comprising Q codes, each including a track number and the elapsed time of a piece of music on the track.
On the other hand, many known digital recording apparatus using a digital audio tape (DAT) or a mini-disk (MD) as recording medium are designed to automatically record start IDs and track numbers on the recording medium for a great convenience of the user on the basis of the CD category identified by decoding the channel status data and the sub-data including the track numbers and the elapsed time of each piece of music recorded on the CD to be replayed as detected by decoding the Q code of the user data when receiving data from the CD player by way of the digital audio interface.
Meanwhile, in recent years, standards for optical disks that are different from known CDs and adapted to record high speed 1-bit digital audio signals for music have been proposed. Audio data addressed by the proposed standards are 1-bit audio signals obtained by subjecting corresponding analog audio signals to a delta-sigma (ΔΣ) modulation process. A 1-bit audio signal is sampled with a very high sampling frequency that is 64 times as high as the sampling frequency of 44.1 KHz of ordinary CDs. The signal is expressed in terms of a very high sampling frequency and a data word length with a very small number of quantization bits and hence characterized by a wide transmission frequency band. Additionally, due to the ΔΣ modulation, it can secure a wide dynamic range in the audio band that is a low frequency band relative to the over-sampling frequency that is 64 times as high as the sampling frequency of ordinary CDs.
An optical disk deals with high speed 1-bit audio signals conforming to the proposed standards for new digital audio signals and shows audio characteristics by far more excellent than those of known CDs. However, a recording system totally different from that of known CDs has to be used for it and hence is not compatible with known CDs in terms of information on the track numbers and the elapsed time of each piece of music as contained in the sub-data as well as other data.
Therefore, when producing a digital audio interface output in a disk replaying apparatus adapted to digital audio signals conforming to the proposed new standards, the category code of the channel status data, the user data and other data generally have to be newly defined and managed.
However, the use of such newly defined data is totally detrimental to the above identified convenience of recording start Ids and track numbers on the recording medium when the data are recorded by way of the digital interface to a known digital recording apparatus.
Particularly, with a reproduction apparatus adapted to both digital audio disks conforming to the new standards and existing CDs, there arises a confusing situation where the above convenience is available when replaying with a CD whereas it is not available when replaying a new disk to a great inconvenience on the part of the user of the apparatus.